Alkylation of aromatic hydrocarbons



Patcnted Sept. 2, 1947 2,426,665 NT OFFICE ALK YLATION- F AROMATICHYDRO: CARBON S Herman S. Bloch, Chicago, Ill., assignor to UniversalOil Products Company, Chicago, 111., a corporation oi Delaware NoDrawing. Application Marches, 1942, Serial Nit-436,314.

Claims.

' This is a continuation-in-part of my co-pending application Serial No.398,194, allied June 16, 1941.

This invention is concerned with the interaction of aromatichydrocarbons with olefins in I in producing molten metal halide mixturesem- 7 the presence of a catalyst. It is more specifically v concernedwith a. simple and easily regulated process involving the use of a,catalyst which is altered only slightly in the course of the reactionbut which catalyzes the desired conversion with a high degree ofefllciency.

Processes for the formation of more highly alkylated aromatichydrocarbons from less highly alkylated aromatic hydrocarbons are ofimportance 'not only from the standpoint of producing high antiknockmotor fuel fractions but for preparing alkylated aromatic hydrocarbonsuseful as intermediates in the production of synthetic organicchemicals.

In one specific embodiment the present invention comprises a processfor' alkylating aromatic hydrocarbons with olefinic hydrocarbons in thepresence of a hydrogen halide and of a molten mixture of metal halidesof the Friedel-Crafts type.

Aromatic hydrocarbons, such as benzene, toluene, other aflrylatedbe'nzenes, naphthalene, alkylated naphthalenes, other poly-nucleararomatics, etc., which are alkylated by olefinic hydrocarbons ashereinafter set forth, may be obtained by the distillation of coal, bythe dehydrogenation of naphthenic hydrocarbons, by the dehydrogenationand/or cyclization of aliphatic hydrocarbons, alkylated aromatichydrocarbons, and alkylated naphthenic hydrocarbons, and by other means.

The olefins utilized for alkylating the aromatic hydrocarbons may beeither normally gaseous or normally liquid. Typical gaseous oleflnscomprise ethylene, propene, and the butenes, while normally liquidolefins may consist of pentenes, hexenes, and higher boiling olefins.Olefinic hydrocarbons suitable for use in alkylation of benzene and itshomologs and polynuclear aromatic hydrocarbons may be obtained fromgaseous and liquid products formed from" the cracking of hydrocarbonoils, by dehydrogenation of paraflins in the presence of catalysts, bythe dehydration of alcohols, 01 from any other source.

The catalyst employed in the process of the present inventioncomprisesmolten mixtures of metal halides of the Friedel-Crafts type.These mixtures of metal halides have relatively low melting points andmay comprise eutectic mixtures having minimum melting points in casesuch mixtures have fusion points corresponding to optimum temperaturesfor the alkylation reaction, but the usable catalysts are not limitedmerely to these eutectic mixtures.

Catalysts oi the Friedel-Crafts type utilizable ployed in the process ofthe present invention include the halides and particularly the chloridesand bromides, of such metals as aluminum, zirconium, zinc, tin,antimony, boron, cadmium,

chromium, iron,-etc., although it is recognized that they are notinterchangeable in any given type of reaction and that not allwillcatalyze certain alkylation reactions. Ofthe metal halides mentioned,aluminum chloride is generally the.

most applicable and zirconium chloride and zinc chloride follow inapproximate order of decreasing activity. The low melting pointmixtures,

which are preferably used in accordance with the I present invention,may include combinations of any of the known'catalysts of theFriedel-Crafts type which have definite activity as catalysts for thealkylation' of aromatic hydrocarbons. It may also be desirable tocomposit proportioned amounts of two Friedel-Crafts type catalysts withanother metal salt Of lesser catalytic activity to form a mixture with arelatively low solidification point. Preferred molten catalysts includea mixture of aluminum chloride and zinc chloride and also a 3-componentcatalyst comprising essentially 'a molten mixture of the chlorides ofaluminum, zinc, and sodium. I

The term solidification point is used in reference to that temperatureat which complete solidification of the salt mixture occurs and in mostcases the temperature of solidification is lower than the reactiontemperatures found to give good results in the alkylation of an aromatichydrocarbon by an olefin in the presence of the particular metal halidemixture employed. In this specification and in the claims the termmolten mixture of metal halides is used. in referring to a mixture ofmetal halides containing a. substantial proportion of a Friedel-Craftstype catalyst and employed at temperatures above the solidificationpoints of said mixtures.

Alkylation operations may be conducted by passing the aromatic andolefinic hydrocarbons upwardly through stationary pools of a moltencatalyst salt mixture or by similarly passing the hydrocarbons upwardlycoun'tercurrent to a descending molten salt mixture in a substantiallyvertical reactor which may or may not contain filling or spacingmaterials such as crushed tragments of relatively inert packing materialas for ed to fractionation and the separated salt mixexample silica, orwhich may contain regularly spaced pans or trays, Alkylation treatmentmay also be carried out by passing liquid or liquefied hydrocarbons anda proportioned amount of molten salt mixture through tubular elementspreferably under conditions of turbulent flow, after which the productsfrom the tubular reactors are discharged into separating chambers fromwhich the hydrocarbon products are directi 01 more.

rate of flow which are utilizable for carrying out the desiredalkyl'ation reaction will vary with the compounds undergoing treatmentand with the nature and composition of the catalyst used, andaccordingly only relatively broad ranges can be given. In generalsuitable alkylation temperoperating pressure may vary from substantiallyatmospheric to approximately 100 atmospheres the particular type ofoperation employed as well as with the characteristics 01 the chargingstock.

In order to favor the production of mono-alkylated aromatic hydrocarbonsand to substantially avoid olefin polymerization, it is advisable tocharge from about 1 to about molecular proportions of aromatichydrocarbon per 1 molecular proportion of olefinic hydrocarbonintroduced to the alkylation reaction.- It is preferable, however, tomaintain a substantial molar excess of aromatic hydrocarbon to olefinichydrocarbon throughout the entire reaction.

It is often desirable to have small but definite amounts of a hydrogenhalide as hydrogen chloride or hydrogen bromide present in a reactionzone so as to promote the catalytic activity of the molten metal halidecatalyst. The presence of hydrogen is advantageous in minimizingundesirable side reactions leading. to the-formation of relatively highmolecular weight compounds.

The following example is introduced'as characteristic of the practicaloperation of the process, althoughit is not presented with the intentionof limiting the scope of the invention in exact correspondence with thenumerical data presented.

80 parts by weight of benzene, 21 parts by weight of propene, and 8.2parts by weight of a catalyst consisting of 65% by weight of aluminumchloride and by weight of zinc chloride having a solidification point of117 C.. were placed in an autoclave and heated with stirring at 125 C.for 1.5 hours. The liquid hydrocarbon product, after separation from thecatalyst, was washed, dried and distilled to separate unconvertedbenzene from alkylated benzene. The 89.2 parts by weight of washed anddried reaction product obtained was thus separated into the followingfractions represented in terms of. the weight per cent based upon thebenzene charged and also upon the propene charged. It is noted thatmono-isopropyl benzene was the major product.

, atures are above the solidification point of the catalyst mixture butbelow about 150 C. The

Flow rates will obviously vary with The bromine number of the entirehydrocare bon product was 1, thus indicating that substantially nopropene polymers were present and that nearly all of the propene had.been utilized to form alkylated benzenes. Inspite or the rather largemechanical loss/which amounted to about 15 'parts by weight of the total101 parts by weight of benzene and propene charged, the alkylatedbenzenes recovered represented approximately 180% of the propenecharged. Of the alkylated benzenes formed and recovered, approximately'7 5% by weight was mono-isopropylbenzene. V :l The character of theinventionand the type of results obtained by its use in practice arevident from the preceding specification and example given, althoughthey are not to be considered as imposingundue limitations upon itsgenerally acting an aromatic hydrocarbon with an olefinic hydrocarbon atan alkylatin'g temperature below about 150 C. in the presence of acatalyst comprising a mixture of a major mol proportion of an aluminumhalide and a minor mol proportion of a zinc halide, said halides beingso proportioned that the mixture thereof is in molten condition at saidalkylating temperature.

2. The process of claim 1 further characterized in that said aromatichydrocarbon comprises a mono-nuclear aromatic hydrocarbon.

' 3. The process of claim 1 further characterized in that said aromatichydrocarbon comprises benzene. I I

4. The process of claim 1 further characterized in that said aromatichydrocarbon comprises a polynuclear aromatic hydrocarbon.

5. The process of claim 1 further characterized in that said olefinichydrocarbon comprises a normally gaseous olefin.

. 6. The process of claim 1 further characterized hydrocarbon at analkylatingtemperatur below about 150 C. in the presence of a catalystcomprising a mixture of a major mol proportion of aluminum chloride anda minor mol proportion of zinc chloride, said chlorides being soproportioned that the mixture thereof is in molten condition at saidalkylating temperature.

8. The process of claim 7 further characterized in that said catalystalso contains sodium chloride.

9. An alkylation process which comprises reacting an aromatichydrocarbon with an olefinic hydrocarbon at an alkylating temperaturebelow about C. in the presence of a catalyst comprising a mixture ofaluminum chloride and zinc chloride in the ratio of about 2 mols ofaluminum chloride per mol of zinc chloride. said mixture being in amolten conditior at said alkylating temperature.

10. An alkylation process which comprises reacting benzene withpropylene at an alkylating temperature below about 150 C. in thepresence of a catalyst comprising a mixture of aluminum chloride andzinc chloride in the ratio of about 2 mols of aluminum chloride per molof zinc chloride, said mixture being in a molten condition at saidalkylating temperature.

' HERMAN s. BLOCH.

(References on followingpage) 5 i 6 REFERENCES CITED I FOREIGN PATENTSThe following references are of record in the Number Country Date fileof this patent: 699,607 Germany Nov. 7, 1940 UNITED STATES PATENTS 5OTHER REFERENCES Number 1 Name Date Thomas, Anhydrous Aluminum Chloride1n 1,878,963 Michel Sept. 20, 1932 Organic Chemistry," pub. ReinholdPub. Co 'p 1,953,702 Davidson Apr. 3, 1934 New York (1941), page 45. (1page). Copy in 2,001,907 Ipatiefl May 21, 1935 Division 31. 2,028,472Rabe Jan. 21. 1936 Grosse et 21., New Metal Halid Catalysts, 2,143,493Stanley et a] Jan. 10, 1939 Jour. Org. Chem. (1937), pages 559-566 (7pages, 2,271,299 Ipatiefl' et a1 Jan. 27, 1942- page 581 especiallypertinent). Patent Omee 2,286,129 Veltman June 9, 1942 Library 260-671.

2,009,108 Eglofl' July 23, 1935 2,370,195 Ross et a1 Feb. 27, 1945 18

